Page 97 - Advances in Textile Biotechnology

78 Advances in textile biotechnology

fibres, such as depilling, scouring or ageing of cotton, enzyme technology

has already proven to be very profitable. Enzyme technology contributes
to the decoupling of economic growth and the use of natural resources
leading to a more sustainable way of life; it enables us to produce more
with less (Wu, 2008). Nevertheless, even though enzymes are produced by
organisms to degrade or synthesize natural substrates, the use of enzymes
is not limited to natural materials. Quite recently it has been demonstrated
by several research groups that enzymes are also able to modify the surfaces
of synthetic textile materials such as polyester and polyamide (for a review
see for example Gübitz and Cavaco-Paulo, 2008).
In this chapter, the focus is on novel promising enzyme applications for

surface modification and hydrolysis of polyester and polyamide fi bres. Clas-
sical methodologies to improve fibre hydrophilicity, like alkaline or acid

hydrolysis, lead to the deterioration of fibre properties such as irreversible
yellowing and loss of resistance (Cribbs and Ogale, 2003; Gübitz and
Cavaco-Paulo, 2003; Miller and Wilmington, 1958; Shukla et al., 1997; Silva,
2002). These processes are based on an ‘all-or-nothing’ mechanism where
the adsorption of high concentrations of chemicals can destroy the surface
of the polymers and negatively affect the favourable bulk properties as well.

Recent studies clearly indicate that the modification of synthetic polymers
with enzymes is an environmentally benign method. Since enzymes are
large molecules their action is restricted to the surface of the fi bres main-
taining their favourable bulk properties. The major advantages of enzymes

in polymer modification, compared with chemical methods, are milder reac-
tion conditions and highly specific non-destructive transformations, tar-

geted to surfaces leading to less fibre damage (Gübitz and Cavaco-Paulo,

2008).
4.1.1 Polyester
Polyesters are a category of polymers containing an ester group, and can
be natural polyesters such as cutin in plants, but most commonly the name
polyester refers to poly(ethylene terephthalate). Poly(ethylene terephtha-
late) (PET) is the most important synthetic fibre owing to its excellent fi bre

properties. Synthesis of polyester is achieved by a polycondensation reac-
tion of a dicarboxylic acid and a diol, or a polycondensation of molecules
containing both a carboxylic acid and an alcohol group. Linear polyester

was first synthesized by Wallace Carothers (1928) at Dupont, who discov-
ered that such polycondensation reactions could be used to produce fi bres.

However, the fibres had a low melting point and poor hydrolytic stability.
Carothers turned to polyamide research. Advancing the early research of
Carothers, John Rex Whinfield and James Tennant Dickson, at the Calico

Printers Association, used aromatic polyesters and discovered PET in 1941.

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